Process for forming a grease containing metal salt of mono and dicarboxylic acids



United States Fatent PROCESS FOR FORMING'A GREASE CONTAINING METAL SALT OF MONO AND DICARBOXYLIC ACIDS Warren C. Pattenden, Courtright, Ontario, Lorne W. Sproule, Sarnia, Ontario, and James H. Norton, Corunna, Ontario, Canada, assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application August 23, 1956 Serial No. 605,726

Claims. (Cl. 25232) This invention relates to greases and grease thickeners and methods of their preparation. Particularly, it relates to a grease thickener which isa soap of a fatty acid and a salt of a dicarboxylic acid and to the method of preparing said grease thickener.

Salts of dicarboxylic acids are known to have high melting points but are usually so indispersible in mineral oil that they have found little use in grease manufacture. However, it has now been found that excellent grease thickeners can be prepared in a lubricating oil base from a mixture of fatty acid soap and the metal salt of a dicarboxylic acid, which salt is obtained by saponification of the diester of the dicarboxylic acid. These thickeners may be prepared by neutralizing a mixture of a fatty acid and a synthetic ester of a dibasic acid with a metal base in either a mineral oil or synthetic oil menstruum. Greases thickened with this new thickener are homogeneous in appearance and have exceptionally high dropping points.

r The synthetic diesters useful in this invention are those formed by the reaction of an aliphatic dicarboxylic acid and a monohydric aliphatic alcohol. These diesters will have the general formula:

ROOC-(CH2)ICOOR1 wherein R and R are alkyl radicals of either straightchain or branched-chain aliphatic saturated monohydric alcohols containing about 1 to 22, e.g. 1 to carbon atoms per molecule, and x is a number of from about 0 to 20, e.g. 4 to 8. The diester molecule will contain a total of about 4 to 64, e.g. 6 to 28 carbon atoms. Also included arediesters prepared from Oxo alcohols, which are an isomeric mixture of highly branched-chain primary alcohols prepared'by'the 0x0 process, which is well known in the art.

The fatty acids useful in carrying out the invention are those fatty acids which are commonly used in preparing grease thickeners. These aliphatic, monocarboxylic acids may be saturated or unsaturated, straight or branchedchain, and may be hydroxy substituted. Generally, they will have about 6 to 30, e.g. 10 to 18 carbon atoms per molecule.

Metal bases of any of the metals commonly used in making grease thickeners may be used in this invention. Generally used are the alkali metal and the alkaline earth metal hydroxides or oxides. These may be used in the form of a hydrate or a water solution thereof.

The menstruum for preparing the thickener may be a mineral oil, a synthetic oil, or a synthetic diester oil of the type used to form the thickener. When the menstruum is a synthetic diester oil, only a portion of the synthetic diester is converted into the thickener, depending upon the amount of alkali which is used. After the grease thickener is formed by the reaction of the metal base with the diester and the fatty acid, then additional e CC tional amounts of any of the other known synthetic'oils,

may be added to form the final grease composition.

In general, the grease composition of the invention will consist of a major proportion, such as 60 to 95 wt. percent, e.g. to 93 wt. percent, Olf a lubricating oil and a thickening amount, such as about 5 to 40 wt. percent, exg. 7 to 25 wt. percent of the grease thickener. The grease thickener, in turn, comprises about 20 to wt. percent, e.g. 30 to 70 wt. percent of the fatty acid soap and about 80 to 20 wt. percent. e.g. 70 to 30 wt. percent, of the dicarboxylic acid salt.

The grease cooking temperature is generally determined by the boiling point of the alcohol formed by the saponification of the diester. The presence of too much alcohol in the final grease reduces the yield and dropping point appreciably. It is therefore desirable to cook the grease sufficiently to remove substantially all of the alcohol which is formed. Generally used are temperatures of about 300 to 500 F., e.g.300 to 400 F.

Lower temperatures could be used if the alcohol was removed under reduced pressure. The mixture is heated for a period of time sufiicient to neutralize the acids, form the thickener, and to evaporate the alcohol formed by the saponification of the diester. This period of time will generally be about 5 to 120 minutes, e.g. 10 to 30 minutes.

Additional lubricating oil and additives may be added to form the final grease product. The grease may then be homogenized through a Manton-Gaulin homogenizer or a similar type of homogenizer, and packaged.

The invention will be better understood by the following illustrations which include the preferred embodiments of the invention.

In order to show that the salt of a dibasic acid and the soap of a fatty acid does not form the same type of thickener as the saponifiedmixture of a fatty acid and diester, the following experiment was made.

of the lithium sebacate as coarse visible particles. At-

tempts to disperse or redisperse the salt of the dicarboxylic acid, once it had separated into'the grainy state,

have been unsuccessful, even whenthe grease was heated to 500 F. Since the. dropping point of'lithium stearat'e" grease is about 370 F., it is apparent that little or no lithium sebacate has been codispersed with the soap.

EXAMPLE I A grease was prepared by mixing 10 grams of stearic acid and 10 grams of di-Z-ethyl hexyl sebacate (equivalent to 4.8 grams of sebacic acid) with 80 grams of a mineral lubricating oil having a viscosity at F. of 300 S.U.S. and a V1. of 70. 3.6 grams of LiOH-H O were added and the mixture was then heated to a temperature of about 400 F and maintained at this temperature for about 15 minutes. The Z-ethylhexanol which formed during the reaction was driven off almost as rapidly as it formed. The grease was then cooled and inspected.

EXAMPLES II TO VI Additional greases were prepared in the manner described in Examplel using the ingredients as noted in the following table. The compositions of the greases of Examples I through VI, and their characteristics, are shown in the following table.

Table 1 Example Number I II III IV V VI Composition in grams:

Stearic Acid 10.0- 10.0 100...... 10.0 10.0 10.0 10.0.

Sebacic Acid- 4.8-

Dl-Z'ethyI hexyl sebacatc 10.0 10.0 10.0 10.0.

Di-Z-ethyl hexyl adipato- 10.0- 10.0

LiOH-HgO 3.6- 3. 3.9- 4.0 4.0- 4.0.

Mineral Oil (Viscosity at 100 F. 80.0 80.0 51.0 80.0 20.0

300 SUS; VI. 70).

Ucon LB-lSOOX 1 80.0

Di-Z-ethyl hexyl adipate (as oil) 60.0

Dow Corning Silicone Fluid 550 Y 76.0. Inspections:

ASTM penetration-77 F 320 250 220 270 AS'IM wkd. penetration 77 F Wt 265 265 310 340 am 250.

ASTM Dropping Point, F 360 500 500+ 485 479 500+ 540+.

Appearance Many Un- Homogc- Homoge Homoge- Homoge- Homoge- Homogedispersed ncous. ncous neous ncous. neous neous. Particles.

Ucon LB-1800X is a water-insoluble polyalkylene glycol type of lubricating fluid which is predominantly polypropylene glycol, and has a viscosity at 100 F. of 1,800 SUS 2 Dow Corning Silicone Fluid 550 is a phenyl methyl polysiloxane having a flash point of 575 F. and a viscosity at 25 C. of

about 100 to 150 centistokes.

As seen from the above table, the greases of the invention had very high dropping points of from 479 F. to above 540 F. and formed homogeneous products. However, the grease formed by the neutralization of the stearic acid and sebacic acid had a dropping point of only 360 F. and contained many undispersed particles.

Various other additives may be added to the grease composition of the invention, such as oxidation inhibitors, dyes, metal deactivators, corrosion inhibitors, deodorants, and so forth, as understood by those skilled in the art.

What is claimed is:

1. A method of preparing a lubricating grease composition comprising a major proportion of a lubricating oil and a thickening amount of a thickener comprising about to 80 wt. percent of a metal soap of a fatty acid and about 80 to 20 wt. percent of a metal salt of a dicarboxylic acid, which comprises heating a mixture of (1) a fatty acid having about 6 to 30 carbon atoms per molecule, (2) a diester of an aliphatic dicarboxylic acid and a monohydric aliphatic alcohol, said diester containing about 4 to 64 carbon atoms per molecule, and (3) a metal base in a lubricating oil menstruum, for a time and temperature sufficient to form a metal salt of said dicarboxylic acid and metal soap of said fatty acid, and to drive ofi substantially all the alcohol which forms during said reaction, then cooling said mixture to obtain said grease composition.

2. A process according to claim 1, wherein said metal base is selected from the group consisting of alkali metal bases and alkaline earth metal bases and mixtures thereof.

3. A process according to claim 1, wherein said lubrieating grease composition comprises about 60 to 95 wt.

percent of a lubricating oil and about 40 to 5.0 wt. percent of said thickener.

4. A process according to claim 1, wherein said mixture is heated to a temperature of about 300 to 500 F. for a time of about 5 to 125 minutes.

5. A process for preparing a lubricating grease composition which comprises heating a mixture of (1) a metal base selected from the group of alkali and alkaline earth metal hydroxides, (2) a fatty acid containing between about 10 to 18 carbon atoms per molecule, and (3) an aliphatic monohydric alcohol diester of an aliphatic dicarboxylic acid containing between about 6 and 28 carbon atoms per molecule, in a lubricating oil menstruum, to a temperature conducive to form a thickener and to drive off substantially all the alcohol which forms during the formation of said thickener, said thickener comprising about 20 to wt. percent of a fatty acid soap, and 80 to 20 wt. percent of dicarboxylic acid salt.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD OF PREPARING A LUBRICATING GREASE COMPOSITION COMPRISING A MAJOR PROPORTION OF A LUBRICATING OIL AND A THICKENING AMOUNT OF A THICKENER COMPRISING ABOUT 20 TO 80 WT. PERCENT OF A METAL SOAP OF A FATTY ACID AND ABOUT 80 TO 20 WT. PERCENT OF A METAL SALT OF A DICARBOXYLIC ACID, WHICH COMPRISES HEATING A MIXTURE OF (1) A FATTY ACID HAVING ABOUT 6 TO 30 CARBON ATOMS PER MOLECULE, (2) A DIESTER OF AN ALIPHATIC DICARBOXYLIC ACID AND A MONOHYDRIC ALIPHATIC ALCOHOL, SAID DIESTER CONTAINING ABOUT 4 TO 64 CARBON ATOMS PER MOLECULE, AND (3) A METAL BASE IN A LUBRICATING OIL MENSTRUUM, FOR A TIME AND TEMPERATURE SUFFICIENT TO FORM A METAL SALT OF SAID DICARBOXYLIC ACID AND METAL SOAP OF SAID FATTY ACID, AND TO DRIVE OF SUBSTANTIALLY ALL THE ALCOHOL WHICH FORMS DURING SAID REACTION THEN COOLING SAID MIXTURE TO OBTAIN SAID GREASE COMPOSITION. 